A toner used in electrophotography, electrostatic recording, electrostatic printing or the like is, for example, in a developing step, once adhered to an image bearing member such as a latent electrostatic image bearing member, on which surface a latent electrostatic image has been formed, is then transferred from the latent electrostatic image onto a transfer medium such as a transfer paper sheet in a transfer step, thereafter, is fixed on the surface of the paper sheet in a fixing step. At that time, since an untransferred toner which remains as residual toner on the latent electrostatic image bearing member with a latent image held on its surface, there is a need to remove the residual toner so as not to prevent the subsequent formation of a latent electrostatic image. In order to remove such residual toner, blade cleaning devices, which are simple in structure and enable obtaining favorable cleanability, are frequently used, however, it is known that the smaller a toner particle size and the closer a toner to a spherical shape, the more difficult it is to remove the toner from a surface of a latent electrostatic image bearing member.
Conventionally, as a dry-process toner used in electrophotography, electrostatic recording, electrostatic printing or the like, a so-called “pulverized toner” is widely used, in which a binder resin or binder resins, such as styrene resin and polyester resin, are fused and kneaded together with a colorant or the like.
However, in recent years, to obtain high-quality images, toners tend to become smaller in size. Therefore, when a toner is made to have a small particle size of 6 μm or less with the use of such a pulverization method, the pulverization efficiency is reduced and the production loss is increased, resulting in a low productivity and high costs.
To avoid the above-mentioned problems, a suspension polymerization method, an emulsion polymerization/flocculation method and the like used for producing a so-called “polymerized toner”, and a toner production method called “polymer dissolution suspension method” which is accompanied by volume shrinkage have been proposed and put in practical use (see Patent Literature 1). The toner production method is excellent in producing toner particles small in size, however, basically, a toner having a substantially spherical shape is produced. In the meanwhile, techniques to make a toner have an irregular shape or non-spherical shape are found out, and it becomes possible to obtain toners to be readily removed by blade cleaning by the use of an emulsion polymerization aggregation method or a polymer dissolution suspension method. Whereas, in these methods, toner particles are formed and produced in an aqueous medium, and thus it is necessary to dry water, which has a large amount of latent heat of vaporization, and a large amount of energy for drying is required. Further, it has been known that these methods assume that a dispersant is used in an aqueous medium, and thus such a dispersant that may impair the electrostatic property of a toner remains on a surface of the toner, causing problems such as adverse effects on environmental stability. Further, in order to remove the dispersant, a great amount of washing water is required. For this reason, toners produced by these methods and these toner production methods are still far from satisfaction.
As an alternative to the methods described above, a method of producing a toner with no use of aqueous medium is proposed which includes the steps of atomizing and jetting a toner composition liquid prepared by dissolving or dispersing a toner composition in a vapor phase to form liquid droplets and removing organic solvents therein to thereby yield toner particles (see Patent Literature 2). Further, a method is proposed which includes the steps of forming minute liquid droplets by utilizing thermal expansion inside nozzles and drying the liquid droplets so as to be solidified (see Patent Literature 3). A method is also proposed in which similar steps to the above method are employed by utilizing an acoustic lens (see Patent Literature 4).
However, these methods have shortcomings that the number of liquid droplets that can be ejected from one nozzle per unit of time is limited, resulting in poor productivity, and it is difficult to prevent the particle size distribution from widening due to coalescence of liquid droplets and therefore the method is also far from satisfaction in terms of monodispersibility. Furthermore, a toner that can be obtained by the method is also disadvantageous in that toner particles are formed in spherical shape due to the surface tension of the toner composition liquid used.    Patent Literature 1 Japanese Patent Application Laid-Open (JP-A) No. 7-152202    Patent Literature 2 Japanese Patent Application Laid-Open (JP-A) No. 2003-262976    Patent Literature 3 Japanese Patent Application Laid-Open (JP-A) No. 2003-280236    Patent Literature 4 Japanese Patent Application Laid-Open (JP-A) No. 2003-262977